TRANSACTIONS OP THE SECTIONS. 113 



Under these views Mr. Carmichael proceeded to offer some general 

 suggestions on the subject of medical treatment in the diseases discussed, 

 and referred to a work on scrofula which he had published in 1806. 



On the Structure of the Teeth, with an Account of the process of their 

 Decay. By James Macartney, M.D., F.R.S., S;c. 



It is universally known that human teeth are composed of two sub- 

 stances, one which determines the figure of the teeth, and another 

 superposed on the surface subjected to friction. Anatomists agree in 

 considering the first of these as the production of the jieculiar structure 

 called the pulp, and the enamel as the secretion of the capsule or mem- 

 branous bag which inclosed the pulp, and the rudiments of the proper 

 substance of the teeth. All the other natural forms of osseous matter, 

 AA'hether they be original or provided for reparation, are preceded by a 

 nidus or preliminary tissue, which is either of a gelatinous or cartila- 

 ginous nature ; for Dr. Macartney has ascertained that the bones of the 

 cranium are produced, like all the others in the body, by the deposition 

 of earthy matter in a cartilaginous substance, which is previously formed 

 between the dura mater and the periosteum of the skull. The teeth 

 therefore in all essential circumstances differ from common bone, and 

 more nearly resemble in their mode of growth, and their natural tem- 

 porary existence, the external coverings of the body. 



The pulps of teeth are known to be very vasculai", and so sensible 

 that they are popularly called the nerves of the teeth. When a pulp 

 is successfully injected with size and vermilion, and examined in a soft 

 state, it appears of a pink colour, as if it were stained throughout, in- 

 stead of deriving its colour from vessels charged with the matter of the 

 injection. In this circumstance it diifers from the capsule, which ex- 

 hibits, after injection, distinct though numerous red vessels. If, how- 

 ever, the pulp be dried on glass, its fine vessels become so apparent, 

 that their arrangement can be easily seen. Dr. Macartney has been en- 

 abled to see the disposition of the nerves in the pulp b)' the same 

 means he has employed for rendering visible the ultimate arrangement 

 of the nervous filaments in the brain. Thus if a section be made of the 

 pulp in a recent state and a solution of alum applied for a few minutes, 

 and the part examined with a lens, a number of white filaments appear 

 at the base of the pulp. These coalescelielow the middle, so as to form a 

 whitish cloud, from whence more distinct filaments radiate in great num- 

 bers towards the surface of the pulp. This appearance may be considered 

 as a ganghon of the most delicate structure in the nervous system, and 

 fully explains the high degree of sensibility possessed by the pulps of 

 teeth, and also the sympathy which is known, to exist between them 

 and the rest of the ner\^ous system. 



After discovering the structure of the pulps of the teeth, and com- 

 paring it with the inferior degree of organization Avhich belongs to the 

 capsule. Dr. Macartney is disposed to attribute the irritation which 

 so often attends the eruption of the teeth to pressure on the pulp, 



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